1. Field of the Invention
The invention concerts cosmetic compositions formulated with menthol and its derivatives.
2. The Related Art
Somatic sensation enables our bodies to feel, ache and react to temperature changes. The reactions occur when skin sensory receptors throughout the body are stimulated by mechanical, physical or chemical contact. Different receptors are responsible for different stimuli; these are categorized as pain, pressure or temperature changes. Special pathways exist for face sensations. The trigeminal nerve is located on the right side of the face. It extends beyond the ear, underneath and branches out towards the cheek area. Properly formulated cosmetic compositions can stimulate the receptors to produce very positive pleasant effects.
One of the oldest stimulants is 1-menthol; it imparts a cooling sensation to the skin. Menthol and related terpenes do not really cool through the effect of latent cold. Actually they heighten the perception of cold in the nerve endings in the skin, so that the surface of skin xe2x80x9cfeels coldxe2x80x9d.
A problem with menthol is dissolving or uniformly dispersing the compound in a cosmetic delivery system. After storage, in many systems menthol has a tendency to crystallize. Severe crystallization leads to granulation effects being perceived by a consumer. Granulation is particularly evident in anhydrous systems.
Accordingly, it is an object of the present invention to provide a cosmetic composition formulated with menthol which avoids crystallization and the aesthetically displeasing effects of granulation.
Another object of the present invention is to provide a cosmetic composition incorporating menthol which enhances pleasant skin sensations while minimizing any negative properties of menthol.
These and other objects of the present invention will become more readily apparent from consideration of the following summary and detailed description.
A cosmetic composition is provided which includes:
(i) from about 0.1 to about 30% of a crosslinked non-emulsifying siloxane elastomer;
(ii) from about 1 to about 80% of a volatile polyorganosiloxane; and
(iii) from about 0.0001 to about 5% of menthol.
Now it has been found that menthol can be suspended without fear of crystallization in a vehicle delivery system of a crosslinked non-emulsifying siloxane elastomer and a volatile polyorganosiloxane. Moreover, the effectiveness of menthol in providing a cooling sensation to the skin is enhanced when delivered in the elastomer and volatile polyorganosiloxane vehicle.
Crosslinked non-emulsifying siloxane elastomers are a first essential element of this invention. They will have an average number molecular weight in excess of 2,000, preferably in excess of 1,000,000 and optimally will range from 10,000 to 20 million. The term xe2x80x9cnon-emulsifyingxe2x80x9d defines a siloxane from which polyoxyalkylene units are absent. Advantageously the elastomers are formed from a divinyl compound, particularly a polymer with at least two free vinyl groups, reacting with Sixe2x80x94H linkages of a polysiloxane backbone such as a molecularly spherical MQ resin. Elastomer compositions are commercially available from the General Electric Company under product designation General Electric Silicone 839 with CTFA name of Cyclomethicone and Vinyl Dimethicone/Methicone Cross Polymer, delivered as 5-7.5% elastomer in a cyclomethicone carrier, and under the designation Polysilicone-11. A related elastomer composition under the CTFA name of Crosslinked Stearyl Methyl Dimethyl Siloxane Copolymer is available as Gransil SR-CYC (25-35% elastomer in cyclomethicone) from Grant Industries, Inc., Elmwood Park, N.J. The commercial products from General Electric and Grant Industries may be further processed by subjecting them to a high pressure (approximately 5,000 psi) treatment in a Sonolator with recycling in 10 to 60 passes. Sonolation achieves a resultant fluid with elastomer average particle size ranging from 0.2 to 10 micron, preferably 0.5 to 5 micron. Viscosity is best when ranging between 300 and 20,000 cps at 25xc2x0 C. as measured by a Brookfield LV Viscometer (size 4 bar. 60 rpm. 15 sec.).
Amounts of the elastomer may range from about 0.1 to about 30%, preferably from about 1 to about 15%, optimally from about 3 to about 10% by weight.
A second element of the present invention is that of a volatile polyorganosiloxane. The term xe2x80x9cvolatilexe2x80x9d refers to those materials having a measurable pressure at ambient conditions. Volatile polyorganosiloxanes useful herein may be cyclic or linear. Preferred cyclic silicones include polydimethylsiloxanes containing from about 3 to about 9 silicon atoms, preferably containing from about 4 to about 5 silicon atoms, generally known as cyclomethicones. Preferred linear silicone oils include the polydimethylsiloxane containing from about 3 to about 9 silicone atoms. The linear volatile silicones generally have viscosities of less then about 5 centistokes at 25xc2x0 C., while the cyclic materials have viscosities of less than about 10 centistokes, the preferable range being from 0.1 to 8 centistokes. Examples of volatile silicone oils useful in the present invention include: Dow Corning 224, Dow Corning 245, Dow Corning 344, Dow Corning 345 and Dow Corning 200 (manufactured by the Dow Corning Corporation); Silicone 7207 and Silicone 7158 (manufactured by the Union Carbide Corporation); and SF1202 (manufactured by General Electric).
Amounts of the volatile polyorganosiloxane will range from about 1 to about 80%, preferably from about 20 to about 70%, optimally from about 30 to about 65% by weight.
Menthol is another essential element of the present invention. The material may be in dextro, levo or racemic form although the levo form is preferred. Amounts may range from about 0.0001 to about 5%, preferably from about 0.01 to about 2%, more preferably from about 0.1 to about 1%, optimally from about 0.2 to about 0.5% by weight of the cosmetic composition.
Cosmetic compositions of the present invention are particularly preferred when in the anhydrous form (less than about 5% water, preferably less than about 1% water). Yet oil and water emulsions may also be suitable for the present invention. Whether anhydrous or emulsion type, compositions of the present invention may further include a variety of pharmaceutically acceptable carriers and skin actives. Amounts of the carrier may range from about 1 to about 95%, preferably from about 5 to about 70%, optimally from about 10 to about 40% by weight. Among the carriers are emollients, water, inorganic powders, foaming agents, surfactants and combinations thereof.
Emollients are substances selected from polyols, esters and hydrocarbons. Polyols suitable for the invention may include propylene glycol, dipropylene glycol, polypropylene glycol, polyethylene glycol, sorbitol, hydroxypropyl sorbitol, hexylene glycol, 1,3-butylene glycol, 1,2,6-hexanetriol, glycerin, ethoxylated glycerin, propoxylated glycerin, xylitol and mixtures thereof.
Esters useful as emollients include:
(1) Alkyl esters of fatty acids having 10 to 20 carbon atoms. Methyl, isopropyl, and butyl esters of fatty acids are useful herein. Examples include hexyl laurate, isohexyl laurate, isohexyl palmitate, isopropyl palmitate, decyl oleate, isodecyl oleate, hexadecyl stearate, decyl stearate, isopropyl isostearate, diisopropyl adipate, diisohexyl adipate, dihexyldecyl adipate, diisopropyl sebacate, lauryl lactate, myristyl lactate, and cetyl lactate. Particularly preferred are C12-C15 alcohol benzoate esters.
(2) Alkenyl esters of fatty acids having 10 to 20 carbon atoms. Examples thereof include oleyl myristate, oleyl stearate and oleyl oleate.
(3) Ether-esters such as fatty acid esters of ethoxylated fatty alcohols.
(4) Polyhydric alcohol esters. Ethylene glycol mono and di-fatty acid esters, diethylene glycol mono- and di-fatty acid esters, polyethylene glycol (200-6000) mono- and di-fatty acid esters, polyglycerol poly-fatty esters, ethoxylated glyceryl monostearate, 1,3-butylene glycol monostearate, 1,3-butylene glycol distearate, polyoxyethylene polyol fatty acid ester, sorbitan fatty acid esters, and polyoxyethylene sorbitan fatty acid esters are satisfactory polyhydric alcohol esters.
(5) Wax esters such as beeswax, spermaceti, myristyl myristate, stearyl stearate.
(6) Sterol esters, of which cholesterol fatty acid esters are examples thereof.
Illustrative hydrocarbons are mineral oil, polyalphaolefins, petrolatum, isoparaffin, polybutenes and mixtures thereof.
Inorganic powders are useful carriers. Examples include clays (such as Montmorillonite, Hectorite, Laponite and Bentonite), talc, mica, silica, alumina, zeolites, sodium sulfate, sodium bicarbonate, sodium carbonate, calcium sulfate and mixtures thereof.
Aerosol propellants may also be used as carriers. Propellants are normally based on volatile hydrocarbons such as propane, butane, isobutane, pentane, isopropane and mixtures thereof. Phillips Petroleum Company is a source of such propellants under trademarks including A31, A32, A51 and A70. Halocarbons including fluorocarbons and dimethyl ether are further widely employed propellants.
Surfactants may constitute at least a portion of the carrier for compositions according to the present invention. These may be selected from nonionic, anionic, cationic or amphoteric emulsifying agents. They may range in amount anywhere from about 0.1 to about 20% by weight. Illustrative nonionic surfactants are alkoxylated compounds based on C10-C22 fatty alcohols and acids and sorbitan. These materials are available, for instance, from the Shell Chemical Company under the Neodol trademark. Copolymers of polyoxypropylenepolyoxyethylene sold by the BASF Corporation under the Pluronic trademark are sometimes also useful. Alkyl polyglycosides available from the Henkel Corporation may also be utilized for purposes of this invention.
Anionic type surfactants include fatty acid soaps, sodium lauryl sulphate, sodium lauryl ether sulphate, alkyl benzene sulphonate, mono- and di-alkyl acid phosphates, sarcosinates, taurates and sodium fatty acyl isethionate.
Amphoteric surfactants include such materials as dialkylamine oxide and various types of betaines (such as cocamidopropyl betaine).
Among the skin actives may be included Vitamin C and its derivatives, alpha- and beta-hydroxycarboxylic acids, retinoids, sunscreens, botanical extracts and sunless tanners. Vitamin C covers ascorbic acid, magnesium ascorbate, ascorbyl tetra fatty esters such as the tetraisopalmitate and similar derivatives. Suitable alpha-hydroxycarboxylic acids include glycolic, lactic, malic and hydroxycaprylic acids. Salicylic acid is representative of the beta-hydroxycarboxylic acids. By the term xe2x80x9cacidsxe2x80x9d is meant to include salts such as alkali metal and ammonium salts thereof. Examples of retinoids include retinol, retinoic acid, retinyl palmitate, retinyl linoleate and retinyl acetate. Botanical extracts include aloe, chamomile, borage, green tea, sage, yarrow, genistein, tulsi, kamala, rosemary, henna, lavender, sandalwood, eucalyptus and combinations thereof. Sunless tanners are particularly represented by dihydroxyacetone and sugars (e.g. xylitol). Sunscreens are those materials having at least one chromophoric group absorbing within the ultraviolet range somewhere from 290 to 400 nm. Particularly useful sunscreens are benzophenone-3, octyl dimethyl PABA, butyl methoxy dibenzoylmethane, octyl methoxycinnamate and octocrylene.
Amounts of the skin actives will depend upon the particular substance. Generally they may range from about 0.0001 to about 30%, preferably from about 0.01 to about 20%, more preferably from about 0.1 to about 10%, optimally from about 0.5 to about 5% by weight of the cosmetic composition.
Minor adjunct ingredients may also be included in cosmetic compositions of this invention. These ingredients may be selected from preservatives, fragrances, anti-foam agents, opacifiers, colorants and mixtures thereof, each in their effective amounts to accomplish their respective functions.
The compositions of the present invention may be applied to a variety of cosmetics. Most particularly they are suitable for skin creams and lotions. However, the compositions will have applicability to hair care products such as shampoos, conditioners, styling gels and hair sprays; shaving products (shaving foam, aftershave lotion); underarm products (antiperspirants and deodorants); personal wash products (toilet bars and body wash liquids); perfume and cologne; and lip care products (lipstick and lip balm), all of which are merely illustrative.
Except in the operating and comparative examples, or where otherwise explicitly indicated, all numbers in this description indicating amounts of material ought to be understood as modified by the word xe2x80x9caboutxe2x80x9d.
The following examples will more fully illustrate the embodiments of this invention. All parts, percentages and proportions referred to herein and in the appended claims are by weight unless otherwise illustrated.